Quote:
Originally Posted by legavroche
Kevin
Would you please expand on the last point you made about the 383 engines, I take it that if you owned one of these you would have considered rebuilding it rather that replacing it with a more modern unit. I have a 411 /S1 with the 383.
Gavin
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Gavin,
I suppose it also depends on what you want to do with it. If you intend to do a basic rebuild/recondition without any improvement (increase in performance) then it wouldn't make much difference. But if you did want to do some tuning then it is more worthwhile on a pre 1971 383.
The main issue is the cylinder heads. The 400 CID engines used by Bristol have a head designed to lower the compression ratio and comply with the pollution controls introduced in the US in the early 1970s. They have a different intake port design so they don't flow anywhere near as well as the early 383 heads, so there's not much point in increasing the valve sizes and doing any porting.
You can of course buy aftermarket heads for the 400 CID engine, but they're not cheap!
I now have a pair of early 383 heads on my 400 CID engine (with larger valves and mild porting). The casting number of the pre smog 383 heads is 2843906, (sometimes referred to as '906 core' heads).
The other benefit of a pre 1971 383 is it will have a forged steel crank shaft, whereas the 400 CID engine has an inferior (cheaper) cast iron crank. This is less of an issue than the heads, although I don't how much you can do with the cast iron crank in terms of welding, machining and polishing.
I was persuaded to "stroke" my engine, so we put a 440 forged steel crank in it, which was "worked" a fair bit to streamline the counterweights.
That said, if you want multi point fuel injection and sophisticated engine management, then it's probably cheaper and certainly a lot less hassle to simply buy a modern replacement engine, regardless of whether you have a 383 or a 400 engine.